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Question 1

What is event handling in Java?

Answer 1

User interaction with frames involves handling events.

Question 2

Give examples of user events in Java.

Answer 2

• Clicking a button
• Typing in a text field
• Dragging the mouse along an area in the frame

Question 3

How are events handled in Java?

Answer 3

Events are handled through listeners.

Question 4

What must a button object be associated with to program functionality?

Answer 4

A listener.

Question 5

What is ActionListener in Java?

Answer 5

An interface in the java.awt.event.* library for handling button actions.

Question 6

What is an inner class?

Answer 6

A class defined within a class, useful for accessing data within the containing class.

Question 7

What is the benefit of using an inner class as a listener?

Answer 7

Listeners need to access frame components.

Question 8

What is the first option for handling multiple buttons in Java?

Answer 8

Create a different listener class for each button.

Question 9

What is the second option for handling multiple buttons?

Answer 9

Use a single listener class for all buttons with different responses.

Question 10

What is the third option for handling multiple buttons?

Answer 10

Create an inner class that implements ActionListener with a constructor that accepts parameters.

Question 11

What are compile-time errors?

Answer 11

Errors detected by the compiler before the program runs, preventing successful compilation.

Question 12

List some causes of compile-time errors.

Answer 12

• Syntax errors
• Type mismatches
• Undefined/Not initialized variables or methods
• Unclosed string literal
• Missing imports
• Missing return statements
• Unreachable statements
• Incorrect method signatures
• Illegal start of expression
• Non-static variable/method cannot be referenced from static context

Question 13

What are runtime errors?

Answer 13

Errors that occur while the program is running, causing crashes or unexpected behavior.

Question 14

List some causes of runtime errors.

Answer 14

• Dividing by zero
• Accessing an invalid array index
• Null references
• File not found
• Illegal operations
• OutOfMemoryError
• StackOverflowError
• NoSuchMethodFoundError
• ClassNotFoundException

Question 15

What is a logic error?

Answer 15

A mistake made by the author that is syntactically correct but leads to unexpected program behavior.

Question 16

What is UML?

Answer 16

Unified Modeling Language, a notation system for object-oriented analysis and design.

Question 17

What type of diagrams do we focus on in UML for Java applications?

Answer 17

Class diagrams to describe classes and their relationships.

Question 18

What does a hollow arrowhead represent in UML?

Answer 18

Inheritance.

Question 19

What does a hollow diamond denote in UML?

Answer 19

Aggregation.

Question 20

What does a straight line represent in UML?

Answer 20

Bi-directional navigability.

Question 21

What is the difference between aggregation and composition?

Answer 21

• Aggregation: parts may be independent of the whole
• Composition: parts are created and destroyed with the whole

Question 22

What does cardinality specify in UML?

Answer 22

The number of objects that may be associated with an object of another class.

Question 23

What does uni-directional navigability look like in UML?

Answer 23

An open arrowhead.

Question 24

What is dependency in UML?

Answer 24

Some classes use other classes but are not related in previously discussed ways.

Question 25

What is the focus of conceptual analysis in UML?

Answer 25

Focus on domain; mapping with code is not strict.

Question 26

What is the visibility notation for public fields in UML?

Answer 26

+

Question 27

How is a derived value indicated in UML?

Answer 27

/ (forward slash)

Question 28

What is the notation for a static field in UML?

Answer 28

Underlined.

Question 29

What symbol is used to denote aggregation in UML?

Answer 29

◇

Question 30

What symbol is used to denote composition in UML?

Answer 30

◆

Question 31

What does the symbol '△' represent in UML?

Answer 31

Inheritance.

Question 32

What does the symbol '⟶' represent in UML?

Answer 32

Dependency.

Question 33

What does the notation '1, *, 1..*' indicate in UML?

Answer 33

Multiplicity.

Question 34

How do you indicate an interface in UML?

Answer 34

<> followed by the name of the interface.

Question 35

What is the notation for an abstract class in UML?

Answer 35

Italicized class name and italicized abstract methods.

Question 36

What does the notation 'balance: double = 0' signify?

Answer 36

balance is private, of type double, and initialized to zero.

Question 37

What does the notation 'books: Book[*]' indicate?

Answer 37

Multiplicity of books.

Question 38

Fill in the blank: A class that is dependent on another class in UML is represented by a _______.

Answer 38

◆ (filled diamond)

Question 39

Fill in the blank: A weak ownership relationship in UML is indicated by a _______.

Answer 39

◇ (hollow diamond)

Question 40

What is a compile-time error in Java?

Answer 40

A compile-time error is an error that occurs during the compilation of the code, preventing it from being successfully compiled.

Question 41

What is a runtime error in Java?

Answer 41

A runtime error is an error that occurs while the program is executing, after successful compilation.

Question 42

True or False: Syntax errors are a type of compile-time error.

Answer 42

True

Question 43

What is an example of a common compile-time error?

Answer 43

Missing semicolon or mismatched parentheses.

Question 44

What type of error occurs when trying to access an array index that is out of bounds?

Answer 44

Runtime error

Question 45

In Java, what does the keyword 'extends' indicate in a class definition?

Answer 45

It indicates inheritance from a parent class.

Question 46

What is UML?

Answer 46

UML stands for Unified Modeling Language, used for modeling software systems.

Question 47

Fill in the blank: In UML, __________ represents a relationship where one class is a part of another class.

Answer 47

Composition

Question 48

What is the difference between aggregation and composition in UML?

Answer 48

Aggregation represents a 'has-a' relationship with independent lifecycle, while composition is a stronger relationship where the child cannot exist without the parent.

Question 49

True or False: In UML diagrams, a solid line with a diamond represents aggregation.

Answer 49

True

Question 50

What is a dependency in UML?

Answer 50

A dependency indicates that one class depends on another class, usually represented with a dashed line.

Question 51

Which error type occurs due to incorrect data types?

Answer 51

Compile-time error

Question 52

True or False: An exception is a type of runtime error in Java.

Answer 52

True

Question 53

What symbol is used to represent inheritance in UML?

Answer 53

A solid line with a closed arrowhead.

Question 54

What is the purpose of the 'super' keyword in Java?

Answer 54

It is used to refer to the superclass of the current object.

Question 55

Fill in the blank: A __________ error causes the program to crash during execution.

Answer 55

Runtime

Question 56

What does it mean when a method is declared with 'throws Exception'?

Answer 56

It indicates that the method may throw an exception that must be handled.

Question 57

What kind of error is caused by dividing by zero in Java?

Answer 57

Runtime error

Question 58

True or False: In UML, a dashed line indicates a generalization relationship.

Answer 58

False

Question 59

What is the main characteristic of a class in a composition relationship?

Answer 59

The child class's lifecycle is tied to the parent class.

Question 60

Which UML relationship is represented by a line with a filled diamond?

Answer 60

Composition

Question 61

What is the purpose of exception handling in Java?

Answer 61

To gracefully handle runtime errors and maintain normal program flow.

Question 62

What are unchecked exceptions in Java?

Answer 62

Exceptions that do not need to be declared in a method's throws clause and can occur at runtime.

Question 63

Fill in the blank: An __________ error is often related to logical mistakes in the code.

Answer 63

Runtime

Question 64

What does it mean if a class is 'abstract' in Java?

Answer 64

It cannot be instantiated and is meant to be subclassed.

Question 65

What keyword is used to handle exceptions in Java?

Answer 65

try

Question 66

True or False: You can catch multiple exceptions in a single catch block in Java.

Answer 66

True

Question 67

What does 'public class MyClass extends BaseClass' signify?

Answer 67

MyClass inherits from BaseClass.

Question 68

What is the outcome of a class that has no main method in Java?

Answer 68

It cannot be executed as a standalone application.

Question 69

True or False: Compile-time errors can be fixed without running the program.

Answer 69

True

Question 70

In UML, how is a class that uses another class represented?

Answer 70

With a dashed line indicating a dependency.

Question 71

What is the purpose of the 'catch' block in exception handling?

Answer 71

To handle the exception thrown by the try block.

Question 72

Fill in the blank: __________ is a relationship where one class contains instances of another class.

Answer 72

Aggregation

Question 73

What does the 'finally' block do in Java exception handling?

Answer 73

It executes code after the try and catch blocks, regardless of whether an exception was thrown.

Question 74

What is the main difference between a checked exception and an unchecked exception?

Answer 74

Checked exceptions must be declared or handled, while unchecked exceptions do not.